Hi, I have a 1986 XJS V12 coupe. The indicators work fine in daylight. Once I turn the headlights on both the left and right indicator lights on the dash light up permanently. The left hand (right hand drive) indicator at both the front and rear are illuminated permanently and do not operate when the indicator stalk is operated. The right hand indicator is not permanently illuminated and works when the indicator stalk is operated.
I have checked the fuses and all the globes. I cannot work out where the wiring for the indicators and parking/headlight come together.


Any ideas would be very welcome.


Regards David

 

I had a problem like that once in my 1972 El Camino. The turn signals worked properly when the headlights were off. When the headlights were on, the turn signals acted crazy.


It turned out to be a bad (weak) electrical ground (somewhere behind the dash as I remember).

 

Right, a poor ground is almost certainly the root cause.

On my XJS the symptom was the tachometer going bonkers when the headlights were on. Poor grounds = weird things happening.

Remove the cluster (easy), clean all contact points on the circuit board, clean the contacts on the cluster harness plug-ins, add a redundant cluster ground. We can provide details if needed.

Cheers
DD

 

Thanks Doug and dcarr,


I have removed the instrument cluster and cleaned all the contacts and added an additional earth. No change in the symptoms.


With the instrument cluster completely removed from the car - electrically isolated (sitting on the passengers seat) I tried the indicators. Exactly the same fault - indicators work fine but when I turn on the lights the left hand indicator on permanently and the right hand works fine?


I am now thinking maybe the tail light housing?


Any thought very welcome.


Cheers David

 

The earths by the lights themselves are just as likely to be the trouble. There are earths and loom connections behind the headlights for the repeaters, as well as the main indicator units' earth wires. Also, the actual bulb holders in the units and the bulbs being a bit iffy can cause the symptoms. I suggest you go over each one at all four corners and clean it, check the bulbs, find the earths and clean up them too.
Greg